Next we look at covariants of binary forms. Recall that the ring
of covariants \(\mathcal {C}(U_j)\) 
of a binary form of degree \(j\)  can be identified
with the ring of invariants \(\mathcal {I}(U_j\oplus U_1)\) 
of \(U_j \oplus U_1\) , see [1]}. If we write
an element of \(U_1\)  as \(l_1x_1+l_2x_2\) , the isomorphism
can be given explicitly by substituting \(l_1=-x_2\)  and \(l_2=x_1\) 
in an invariant of \(U_j\oplus U_1\) .
